text: Hofmann's research dealt in particular with the chemistry of clay minerals, as well as with pigments and ancient ceramics. In the 1930s, he and Kurd Endell examined the structure of clay minerals using X-ray structure analysis, among other things. Among other things, they published in 1933 on the structure of the clay mineral montmorillonite. Together with Kurd Endell, he also found the reason why German bentonites, in contrast to those from Wyoming in the USA, were not suitable for the construction industry - the cation between the silicate layers was sodium in American bentonite, and calcium or magnesium in German deposits. By adding sodium carbonate, however, German bentonite could also be used, which they patented in 1934/35. Hofmann also examined other clays (such as kaolin) to see how the properties (e.g. swelling behavior) changed with the cations between the silicate layers when absorbing water.
  Continuing the work of Peter Debye and Paul Scherrer, who analyzed the structure of graphite and diamond with X-rays, he studied lustrous carbon and graphite oxide, among other things, and he studied, for example, the absorptivity and catalytic activity of graphite and graphite growth at high temperatures. This also brought him into contact with industry, for example with Siemens-Plania in Berlin before World War II. In 1941, together with Manfred von Ardenne, he examined soot particles using an electron microscope and found them to be made up of chains of spherical carbon structures.